1. Field of the Invention
The present invention relates to a light compensation scheme, an optical machine device, a display system and a method for light compensation, and more particularly, to an optical machine device which is capable of actively compensating uniformity of illumination by a light compensation scheme.
2. Description of the Prior Art
Presently, a good few display systems, such as a projector, a projecting display or a high-definition television (HDTV) system, adapt a Liquid Crystal on Silicon (LCoS) technology which is adequate for a high-resolution, large-screen display sized to be slim and rendering higher brightness and contrast than the conventional liquid crystal display (LCD) did. Such a LCoS display system primarily includes an illumination module, a polarizing beam splitter (PBS), a active-matrix LCoS panel, at least one color separation set, lots of optical lenses, a projecting lens and a screen, wherein the illumination module, the polarizing beam splitter, the active-matrix LCoS panel, the at least one color separation set, the optical lenses and the projecting lens can constitute an optical machine device or a so-called “optical engine”, with corresponding beam pathways built among the above-mentioned elements. The illumination modules of the most conventional LCoS display systems employ a monochromatic light source like an arc lamp to emit monochromatic beams. Each of the monochromatic beams needs to pass through the at least one color separation set (e.g. a color filter) to be separated into different-color beams (e.g. the red (R), green (G) and blue (B) of three primary colors). Afterward the different-color beams are transmitted via the corresponding optical lenses and the polarizing beam splitter to the LCoS panel. However, the above-mentioned arrangements might easily invoke higher optical losses and lower luminosities among the whole during light transmission, especially in that the several optical lenses are often used to transmit different-color beams each which must be ensured in accurate alignment with the corresponding beam pathways, whereby their beam pathway designs become more complicated and costly. When the different-color beams are polarized by the polarizing beam splitter to emit the corresponding polarized beams incident to the LCoS panel, a plurality of pixel electrodes arranged in active matrixes of the LCoS panel possess direction change of liquid crystals (LCs) based on a specific voltage applied on modulating the different-color polarized beams. Then the different-color polarized beams are separated into corresponding reflective beams for forming a full-color image. The different-color reflective beams of the image are reflected from the LCoS panel to the screen via the polarizing beam splitter and the projecting lens so that an imaging frame is visibly displayed on the screen. In another case of replacing the monochromatic light source with a driven-by-motor color wheel to separate different-color beams, many more lens sets are accordingly used for the separated respective different-color beams. However, this causes the whole beam path design much more complicated and occupying more optical engine space, and even its optical loss and the element costs increased, greatly. In another case of using three LCoS panels for individually processing different-color beams (e.g. red (R), green (G) and blue (B) of three primary colors), the amounts of full-reflective optical lenses and full-transmissive optical lenses in use need to increase, accordingly and each of the different-color beams correspondingly meets more complicated beam pathways. That would be more costly.
Besides even the monochromatic light source emits beams via the same optical lens, the luminous intensities of the different-color beams reflected from the LCoS panel might be uneven if the angles of emitting the respective beams are different, the beam pathways where the different-color beams pass from the monochromatic light source to the LCoS panel are different or the performances of the respective light sources are inconsistent. For an example of uneven luminosities, a luminosity difference occurs between a central region and a boundary region on a surface of the LCoS panel. As a coordinate diagram shown in FIG. 1, the respective luminosity values (L) of the beam transmitted from the monochromatic light source to the LCoS panel via the same optical lens appear in unevenness, in comparison with a characteristic value (K) representing a finished light source which is qualified.
Currently, the illumination modules of many conventional large-sized display systems employ a plurality of different-color light sources (e.g. the red (R), green (G) and blue (B) light emitting diodes (LEDs)) to be pointolites. There have some inherent defects that both luminance efficiency and uniform illumination of the LED pointolites are controlled more difficult than a linear light source revealed by a conventional cold cathode fluorescent lamp (CCFL). To achieve the optimal uniform illumination, it becomes essential to pick matching-characteristic ones from the finished LEDs. Such a picking-product step would cause the cost increased. If the luminosities revealed from the different-color LEDs are uneven, an illustration shown in FIG. 2a may happen that a luminosity value (R) of the red light source is higher than the characteristic value (K) representing a qualified product but the luminosity values of the other light sources (e.g. the green and blue lights) is lower than the characteristic value (K). Thus, there is a luminosity difference occurring among these light sources. Besides if the locations of the different-color light sources are different or inaccurate, for example, one of the different-color light sources is allocated askew upwardly but another one is allocated askew downwardly, this would make different illuminative angles where the respective beams of the different-color light sources pass through the optical lens. Furthermore, due to the optical losses during reflection and/or transmittance of the beams through the corresponding lens allocated on the respective beam pathways, the luminous intensities (or the luminosity value) of the different-color beams incident into the LCoS panel are invoked uneven, as the result shown in FIG. 2b.